Planet ‘devoured in secret’ by its own sun

WASP-12

A planet roughly 1.4 times the size of Jupiter is being consumed by its own star behind a shroud thanks to a magnesium veil absorbing all of certain light wavelengths, according to new observations by the Hubble Space Telescope (HST).

WASP-12 b, originally spotted in 2008, is a gas giant planet orbiting extremely close to its parent star. The distance between the star and planet is so small that the planet completes an orbit of its star in just over one Earth day. This proximity has “boiled off” a superheated gas cloud roughly three times the radius of Jupiter which feeds the star. However, some of this gas is moving out towards interstellar space, creating a shroud around the star.

The gas shroud is thin, and barely noticeable in optical light, but the new observations were made with HST using near-UV light. The team discovered that one element in the cloud is magnesium, which is extremely efficient at absorbing near-UV light. These wavelengths are extremely sensitive to the presence of tenuous gas, and in them the star can appear completely invisible. The study was made by researchers from the UK’s Wide Angle Search for Planets (WASP) consortium, who originally found the planet in 2008, as well experts on the Cosmic Origins Spectrograph aboard the HST, stellar activity, and interstellar absorption from the Center for Astrophysics and Space Astronomy at the University of Colorado.

Senior Lecturer in Astronomy at The Open University Dr Carole Haswell, who led the study, said that a structure like this had never before been observed around a star, adding: “It's as though a veil has been drawn over the planet's demise.”

The paper, Near-UV Absorption, Chromospheric Activity, and Star-Planet Interactions in the WASP-12 system Haswell et al 2012, will be published in The Astrophysical Journal on the 20th of November.

Notes to the editorAbout The Open UniversityThe Open University (OU) is the largest academic institution in the UK and a world leader in flexible distance learning. Since it began in 1969, the OU has taught more than 1.8 million students and has more than 263,000 current students, including over 15,000 overseas.

The OU came top for student satisfaction in the National Student Survey this year, and has been in the top three universities every year since the survey began in 2005. In 2011/12 it had a 93 per cent satisfaction rating. Over 70% of students are in full-time or part-time employment, and four out of five FTSE 100 companies have sponsored staff to take OU courses.

In the UK’s latest Research Assessment Exercise (RAE 2008) the Open University was ranked in the top third of UK higher education institutions. More than 50% of OU research was assessed in the RAE as internationally excellent, with 14% as world leading.

Regarded as Britain’s major e-learning institution, the OU is a world leader in developing technology to increase access to education on a global scale. Its vast ‘open content portfolio’ includes free study units on OpenLearn, which has had more than 23 million visits, and materials on iTunes U, which has recorded over 56 million downloads. The OU has a 41 year partnership with the BBC which has moved from late-night lectures in the 1970s to prime-time programmes such as Frozen Planet, Bang Goes the Theory, James May’s Big Ideas and The Money Programme.